Chapter 12 Elements and Their Properties This beautiful diamond is made up of atoms of the element carbon. Most matter can be described by the elements of which it is made. Each element has distinct properties. Elements arranged together on the periodic table have similar properties. Knowing the properties of elements allows us to use them in a variety of practical ways. This chapter will describe groups of elements and help you to learn how they are related. EXPLOREï¿½ ACTIVITY Some clues are in color. 1. Using tongs, carefully hold a clean paper clip in the hottest part of a lab burner flame until no additional color is observed. 2. Dip the hot paper clip into a solution of copper (II) sulfate. 3. Using the tongs, repeat step 1, observing any color change. 4. Repeat these steps using solutions of strontium chloride and sodium chloride. Observe: How can observation of color be used to identify elements in solutions? Based on your observations, devise a plan in your Science Journal to determine whether chlorine or strontium was giving the color you observed in a particular test. Previewing Science Skills In the Skill Builders, you will interpret scientific illustrations, make and use a graph, and map concepts.

In the Activities, you will observe, compare, predict, infer, and build a model. In the MiniLABs, you will observe and draw conclusions 329 Describe the properties of a typical metal. Identify the alkali and alkaline earth metals. Differentiate among three groups of transition elements. Properties of Metals Have you ever seen very old jewelry or statues made of gold and copper? These were two of the first metals used thousands of years ago. The use of silver and tin soon followed. Then came iron. But aluminumï¿½the metal used in thousands of soft-drink cansï¿½wasn't discovered until a little more than 100 years ago. Gold, copper, silver, tin, iron, and aluminum are typical metals. What do these and other metals have in common? Most metals are hard, shiny solids. Metals are also good conductors of both heat and electricity. These properties make metals suitable for uses ranging from kitchen pots and pans to wires for electric appliances. Because metals reflect light well, they are also used in mirrors. Metals are malleable, which means they can be hammered or rolled into sheets. The gold leaf shown in Figure 12-1 is used for elaborate decoration.

Metals are also ductile, which means they can be drawn into wires like the ones shown in Figure 12-2. The atoms of metals generally have from one to three electrons in their outer energy levels. Metals tend to give up electrons easily. Remember from Chapter 11 what happens when metals combine with nonmetals? The atoms of the metals tend to lose electrons to the atoms of nonmetals, and form ionic bonds. The second type of bond you studied is the covalent bond, which generally forms between atoms of nonmetals. Figure 12-1 Gold can be hammered into thin sheets. The sheets, called gold leaf, can be applied to many types of surfaces. What is this property of metals called? 330 Figure 12-2 Metals can be drawn into wires. This property is called ductility. The gauge of a wire is related to its thickness. A large number indicates a thinner wire. Bonding in Metals A third type of bonding, neither ionic nor covalent, occurs among the atoms in a metal. In metallic bonding, positively charged metallic ions are surrounded by a "sea of electrons." Outer-level electrons are not held tightly to their particular nucleus.

Rather, the electrons move freely among many positively charged ions. The electrons form a cloud around the ions of the metal as shown in Figure 12-3. Figure 12-3 In metallic bonding, the moving outer electrons, depicted by the cloud, cover the rest of the atoms no matter where the electrons are in the metal. How does this differ from covalent bonding? Metallic bonding explains many of the properties of metals. For example, when a metal is hammered into a sheet or drawn into a wire, it does not break because the ions are in layers that slide past one another. And because the outer-level electrons are weakly held, metals are good conductors of electricity. Look at the periodic table on pages 286-287. How many of the elements in the table are classified as metals? Except for hydrogen, all the elements in Groups 1 through 12 are metals. You will learn about metals in some of these groups and others throughout this chapter. MiniLAB How can metallic bonding explain the flexibility of metals? Procedure 1. Using tongs, carefully hold two pieces of metal wire in a lab burner flame until they are glowing red-hot. 2.

Quickly drop one of the hot wires into a beaker of cold water. Allow it to cool. 3. Allow the other hot wire to cool slowly. 4. Hold the ends of each piece of cooled wire and bend them. Analysis 1. What do you observe about the flexibility of the two cooled wires? 2. How can metallic bonding be used to help explain your observations? 331 The Alkali Metals The elements in Group 1 of the periodic table are the alkali metals. Like other metals, Group 1 metals are shiny, malleable, and ductile. They are good conductors of both heat and electricity. The alkali metals are highly reactive metals. Figure 12-4 shows how reactive they are with water. As a result of their reactivity, why would you expect to find the alkali metals in nature only in the form of compounds? Each atom of an alkali metal has one electron in its outer energy level. This electron is given up when an alkali metal combines with another atom. The result is a positively charged ion in a compound such as sodium chloride, NaCI, or potassium bromide, KBr. Alkali metals and their compounds have many uses.

You and other living things need potassium and sodium compoundsï¿½such as table salt, NaClï¿½to stay healthy. Doctors use lithium compounds to treat bipolar disorder. The operation of some photocells depends upon rubidium or cesium compounds. Francium, the last element in Group 1, is extremely rare and also radioactive. The nucleus of a radioactive element breaks down and gives off particles and energy. You will study radioactive elements later. Figure 12-4 Alkali metals are very reactive. Li, Na, K, and Cs react violently in water. Why wouldn't the reaction of francium be shown in the photo? 332 The Alkaline Earth Metals The alkaline earth metals make up Group 2 of the periodic table. Like the alkali metals, these metals are shiny, malleable, ductile, and so reactive that they are not found free in nature. Each atom of an alkaline earth metal has two electrons in its outer energy level. These electrons are given up when an alkaline earth metal combines with another element. The result is a positively charged ion in a compound such as calcium fluoride, CaF2.

Bats, Batteries, and Beryls Emeralds and aquamarines are gemstone forms of beryl, a mineral that contains beryllium. Do you watch fireworks on the Fourth of July? The brilliant red in fireworks is produced by compounds of strontium. Magnesium can be made into a fine wire that burns so brightly that it is used in some photographic flashbulbs. Magnesium metal is also used in fireworks to produce brilliant white. Magnesium's lightness and strength account for its use in cars, planes, and spacecraft. Magnesium is also used to make such things as household ladders and baseball and softball bats, such as the one shown in Figure 12-5. Most life on Earth depends upon chlorophyll, a magnesium compound that enables plants to make food. Calcium is seldom used as a free metal, but its compounds are needed for life. Calcium phosphate in your bones helps make them strong. Marble and limestone are calcium carbonate. Figure 12-5 Alkaline earth metals are found in these objects. Which metals are represented here? 333 Some barium compounds are used to diagnose digestive disorders. The patient swallows a barium compound, which can absorb X rays.

As the barium compound goes through the digestive tract, a doctor can study the X rays. Radium, the last element in Group 2, is radioactive. It was once used to treat cancers. Today, other radioactive substances are replacing radium in cancer therapy. Transition Elements An iron nail, a copper wire, and a silver dime are examples of objects made from transition elements. The transition elements are those elements in Groups 3 through 12 of the periodic table. Typical transition elements are metals and have one or two electrons in the outer energy level. These metals are less active than those in Groups 1 and 2. The gems in Figure 12-6 contain brightly colored compounds of transition elements. Brilliant cadmium yellow and cobalt blue paint pigments are made from compounds of transition elements. But cadmium and cobalt paints are so toxic that their use is now limited. Figure 12-6 The colors of these gems are due to compounds of transition elements. Iron, Cobalt, and Nickel Iron, cobalt, and nickel form a unique cluster of transition elements. The first elements in Groups 8, 9, and 10, respectively, are known as the iron triad.

The elements of the triad are the only ones known to create a magnetic field. 334 Iron is second only to aluminum among the metals in abundance in Earth's crust. As the main component of steel, iron is the most widely used of all metals. Some steels also contain cobalt. Nickel is added to other metals to give them strength. Nickel is also often used to give a shiny, protective coating to other metals. Copper, Silver, and Gold Can you name the main metals in the coins in Figure 12-7 on page 336? They are copper, silver, and goldï¿½the three elements in Group 11. They are so unreactive that they can be found as elements in nature. For centuries, these metals have been widely used as coins. For this reason, they are known as the coinage metals. Copper is often used in electric wiring because of its superior ability to conduct electricity and 335 its relatively low cost. Can you imagine a world without photographs and movies? Because silver iodide and silver bromide break down when exposed to light, these compounds are used to make photographic film and paper. Much silver is also used in jewelry.

The yellow color, relative softness, and rarity of gold account for its use in jewelry. Figure 12-7 Some Group 11 elements are used to make coins. (from page 335) USING TECHNOLOGY Metals with Memory What would a radio antenna in space have in common with your smile? They both benefit from nitinol. Nitinol is a metal alloy with a memory. Nitinol is the name given to the metal mixture, or alloy, made from the transition elements nickel and titanium. The alloy, which is made into a preset shape, can later be deformed into a new shape. Practical Uses So how is this used on teeth? The wire connecting brackets in braces is nitinol. If the teeth are not properly aligned, the wire will be deformed from its preset shape. Soon, the wire will attempt to return to its original shape, putting pressure on the bracketed teeth and moving them. Engineers also made use of nitinol when a large radio antenna was compactly folded during launch into space. Once in orbit, the metal with a memory absorbed heat and began to unfold into its original shape. This property of nitinol is also useful in eyeglass frames.

Think Critically: Elements that can form shape-memory alloys, SMAs, are found in Groups 3 through 12 on the periodic table. List other properties of these elements in your Science Journal. Zinc, Cadmium, and Mercury Zinc, cadmium, and mercury make up Group 12 of the periodic table. Zinc combines with oxygen in the air to form a thin protective coating of zinc oxide on the surface of the metal. Zinc is often used to coat, or plate, other metals, such as iron. Cadmium is also used in plating and in rechargeable batteries. Mercury is a silvery, liquid metal used in thermometers, thermostats, switches, and batteries. Mercury is poisonous, and mercury compounds can accumulate in the body. People have died of mercury poisoning that resulted from eating fish from mercury-contaminated water. Look at the periodic table on pages 286-287. Which elements do you think of as being typical metals? Transition elements are the most familiar because they occur in nature as elements. Group 1 and Group 2 metals are found in nature only in compounds.

Metals in the Crust When we examine pictures of metals and their compounds, we are really seeing only half the story. Where are metals found? How do we obtain them? Earth's crust contains many compounds and a few examples of uncombined metals such as gold and copper. Metals must be dug, or mined, from Earth's hardened outer layer. 336 Due to varying conditions in different areas, some metals are deposited more in one place than in another. For example, most of the world's platinum is found in South Africa. Large amounts of cobalt can be found in Morocco, Zaire, and Canada. Chromium is important to the United States, but we must import most of it from South Africa, the Philippines, and Turkey. Ores: Minerals and Mixtures Metals in Earth's crust that are in a combined form are found in ores. Typically, an ore consists of a metal compound, or mineral, within a mixture of clay or rock. Lead metal is usually found combined with sulfur in the form of galena, or lead sulfide. After an ore is mined and brought from Earth's surface, minerals must be separated from the rock. Then the mineral is often converted to another chemical form.

Galena is converted to lead oxide. This step involves heat and is called roasting. Finally, the metal is refined into a pure form. It may later be alloyed with other metals. Removing the waste rock can be very expensive. If the cost of removing the waste rock gets higher than the value of the desired material, the mineral will no longer be classified as an ore. USING MATH Several elements are present in Earth's crust. The approximate percentage of each element is as follows: Oxygen, 46.6 Potassium, 2.6 Magnesium, 2.1 Other elements include titanium, hydrogen, phosphorus, and manganese, which account for 1.5 percent. Make a circle graph of these data. Section Wrap-up Review 1. You are given a piece of the element palladium. How would you test it to see if it is a metal? 2. On the periodic table, how does the arrangement of the iron triad differ from the arrangements of the coinage metals and of the zinc group? 3. Think Critically: If X stands for a metal, how can you tell from the formulas XCl and XCl2 which compound contains an alkali metal and which contains an alkaline earth metal?

Skill Builder Interpreting Scientific Illustrations Draw dot diagrams to show the similarity among chlorides of three alkali metals: lithium chloride, sodium chloride, and potassium chloride. If you need help, refer to Interpreting Scientific Illustrations in the Skill Handbook. Science Journal We encounter examples of metals nearly everywhere. In your Science Journal, write a paragraph describing how a specific metallic element has an effect in your life. Which group is that metal in on the periodic table? 337 12.2 TECHNOLOGY:ï¿½ New Elements, New Properties Science Words Distinguish among elements classified as lanthanides, actinides, and transuranium elements. Determine the uses of transuranium elements. Compare the pros and cons of making new elements. Elements Beyond 92 What if you made something that always fell apart? You might think you were not successful. Yet nuclear scientists are learning to do just that. By combining existing elements with fast-moving particles, they have been successful at creating elements not typically found on Earth. Except for one, the short-lived elements have more than 92 protons. All of these synthetic elements are unstable and fall apart quickly.

Elements having more than 92 protons, the atomic number of uranium, are called transuranium elements. Additions to the Family If you look at the periodic table on pages 286-287, you will see breaks in periods 6 and 7. The first break includes a series of 14 elements with atomic numbers of 58-71. The elements in this series are known as the lanthanides. The second break includes elements with atomic numbers ranging from 90103. These elements are known as actinides. Ten synthetic elements are found in the actinide series. Where are the others placed on the periodic table? Technetium is element number 43. The newest synthetic elements are placed in period 7. Synthesis: A Smashing Success If atoms and other particles are smashed together with sufficient force, they will fuse to form a new identity. For example, neptunium, element 93, can be made by bombarding 338 uranium with neutrons. Atoms of neptunium do not stay together for long. Half of the synthesized atoms disintegrate in about two days.

This may not sound useful, but when neptunium atoms fall apart, they form plutonium. This highly toxic element has been used in control rods of nuclear reactors, such as those shown in Figure 12-8, and in bombs. Plutonium can also be changed to americium, element 95. This transuranium element is used in some home smoke detectors such as the one in Figure 12-9. Figure 12-8 (from page 338) These fuel rods contain plutonium, element 84. How would plutonium be classified? Figure 12-9 Synthesis of elements has resulted in life-saving smoke detectors. Why make elements? By studying how the synthesized elements form and fall apart, we can gain an understanding of the forces holding other elements together. When these atoms fall apart, they are said to be radioactive. Technetium's radioactivity makes it ideal for many medical applications. At this time, many of the synthetic elements, once made, last only small fractions of seconds and can be made only in small amounts. However, further advances in technology may bring production up to larger amounts.

The as-yet-undiscovered applications could prove to be more valuable than their costs. Section Wrap-up 1. How is an element classified as a transuranium element? 2. Where are the actinides located on the periodic table? interNET CONNECTION Some people are concerned about the use of radioactive elements such as americium in smoke detectors and other products. Visit the Chapter 12 Internet Connection at Glencoe Online Science, for a link to more information about radioactive elements. 339 Recognize hydrogen as a nonmetal. Compare and contrast properties of the halogens. Describe properties and uses of the noble gases. Properties of Nonmetals Figure 12-10 shows that you're mostly made of oxygen, carbon, hydrogen, and nitrogen. Calcium, a metal, and other elements make up the remaining four percent of your body's weight. Phosphorus, sulfur, and chlorine are among other elements found in your body. These elements are classified as nonmetals. Look at the periodic table on pages 286 and 287. How many elements are nonmetals? Notice that most nonmetals are gases at room temperature. Several nonmetals are solids, and one nonmetal is a liquid.

Figure 12-10 Humans are made up of mostly nonmetals. Attracting Electrons In contrast to metals, solid nonmetals are dull. Because they are brittle and powdery, they are neither malleable nor ductile. The electrons in most nonmetals are tightly attracted and are restricted to one atom. So, as a group, nonmetals are poor conductors of heat and electricity. Most nonmetals form both ionic and covalent compounds. Examples of these two kinds of compounds are shown in Figure 12-11. When nonmetals gain electrons from metals, the nonmetals become negative ions in ionic compounds. An example of such an ionic compound is potassium iodide, KI, 340 which is often added to table salt. KI is formed from the nonmetal iodine and the metal potassium. On the other hand, when bonded with other nonmetals, atoms of nonmetals usually share electrons and form covalent compounds. An example is ammonia, NH3, the gas you can smell when you open a bottle of household ammonia. The noble gases, Group 18, make up the only group of elements that are all nonmetals.

Group 17 elements, except for astatine, are also nonmetals. Several other nonmetals, found in Groups 13 through 16, will be discussed later. Except for hydrogen, all of the nonmetals are located on the right side of the periodic table. Figureï¿½ 12-11 Nonmetals form both ionic and covalent compounds. Which picture depicts which kind of bonding? Hydrogen Do you know that approximately 90 percent of all the atoms in the universe are hydrogen? Most hydrogen on Earth is found in the compound water. When water is broken down into its elements, hydrogen forms as a gas made up of diatomic molecules. A diatomic molecule consists of two atoms of the same element. Thus, the formula for hydrogen gas is H2, shown in Figure 12-12. Small, But Active Hydrogen is highly reactive. A hydrogen atom has a single electron, which the atom shares when it combines with other nonmetals. Hydrogen burns in oxygen to form water, H2O. In forming water, hydrogen shares electrons with oxygen. Hydrogen also shares electrons with chlorine to produce hydrogen chloride, HCl.

Hydrogen may gain an electron when it combines with alkali and alkaline earth metals. The compounds formed are hydrides, such as sodium hydride, NaH. Figure 12-12 Hydrogen gas, which consists of diatomic molecules, combines with oxygen in an oxyhydrogen torch. 341 The Halogens Look how bright the high- tech lamp is in Figure 12-13. Its light and that of the head-lights of some cars are supplied by halogen lightbulbs. These bulbs contain small amounts of bromine or iodine. These elements, as well as fluorine, chlorine, and astatine, are called halogens and are found in Group 17. Because an atom of a halogen has seven electrons in its outer energy level, only one electron is needed to complete this energy level. If a halogen gains an electron from a metal, an ionic compound, called a salt, is formed. The word halogen means "salt former." In the gaseous state, the halogens form very reactive diatomic covalent molecules and can be identified by their distinctive colors, as shown in Figure 12-14.

Fluorine is the most chemically active of all the elements. Hydrofluoric acid, a mixture of hydrogen fluoride and water, is used to etch glass and to frost the inner surfaces of light- bulbs. Other fluorides are added to toothpastes and to city water systems to prevent tooth decay. Does your community add fluorides to its water? Figure 12-13 The halogens bromine and iodine are used in the bulbs of halogen lamps. Figure 12-14 These are the gaseous halogens chlorine, bromine, and iodine. MiniLAB Can you detect chlorine in your drinking water? Procedure 1. In separate test tubes, obtain 2 mL of chloride standard solution, distilled water, and drinking water. 2. Carefully add five drops of silver nitrate solution to each and stir. CAUTION: Avoid contact with the silver nitrate solution. Analysis 1. Which solution will definitely show a presence of chloride? How did this result compare to the result with distilled water? 2. Which result most resembled your drinking water? CONNECT TO EARTH SCIENCE Compounds called chlorofluorocarbons are used in refrigeration systems.

If released, these compounds destroy ozone in the atmosphere. Draw the electron dot diagram for CF2Cl2 in your Science Journal. 342 Uses of Halogens The odor near swimming pools is the odor of chlorine. Chlorine compounds are used to disinfect water. Chlorine, the most abundant halogen, is obtained from seawater. Household and industrial bleaches used to whiten flour and paper also contain chlorine compounds. Bromine, the only nonmetal that is liquid at room temperature, is extracted from compounds in seawater. Other bromine compounds are used as dyes in cosmetics, such as the lipsticks shown in Figure 12-15. Iodine, a shiny gray solid at room temperature, is obtained from seawater. When heated, iodine changes directly to a purple vapor. The process of a solid changing directly to a vapor without forming a liquid is called sublimation as shown in Figure 12-16. Recall that sublimation accounts for ice cubes shrinking in freezers. Iodine is essential in your diet for the production of the hormone thyroxin and to prevent goiter, an enlarging of the thyroid gland in the neck.

Astatine, the last member of Group 17, is radioactive and rare. But it has many properties similar to those of the other halogens. Figure 12-15 Dyes in some cosmetics contain bromine compounds. What unique physical property does bromine have? Figure 12-16 Ice and dust form the body of a comet. The ice undergoes sublimation, forming the gases contained in the tail of the comet. This particular comet is Hale-Bopp, which was visible from Earth for several months in 1997. The Noble Gases Why are the noble gases called noble? It was known that these gases did not naturally form compounds. Thus, they were thought of as the nobility of elements because nobles did not mix with common folk. However, in the early 1960s, scientists were able to prepare some compounds of noble gases. 343 As you recall, each element in Group 18 is stable because its outer energy level is full. The stability of the noble gases plays an important role in their uses, such as those shown in Figure 12-17.

Both the halogens and the noble gases illustrate that each element in a group has some similar properties but also has unique properties and uses. Figure 12-17 Noble gases are used to produce laser light shows. Section Wrap-up Review 1. What are two ways in which hydrogen combines with other elements? 2. Rank the following nonmetals from lowest number of electrons in the outer level to highest: Cl-, H+, He, H. 3. What property of noble gases makes them useful? 4. Think Critically: Why must hydrofluoric acid always be stored in plastic bottles? Skill Builder Interpreting Data Within the following compounds, identify the nonmetal and list its oxidation number: MgO, NaH, AlBr3, FeS. If you need help, refer to Interpreting Data in your Skill Handbook. Using Computers Graphing Prepare a bar graph comparing nonmetals and metals as solids, liquids, and gases at room temperature. 344 Activity 12-1 What type is it? Suppose you want an element for a certain use. You may be able to use a metal but not a nonmetal. Or maybe a nonmetal better meets your needs.

In this activity, you will test several metals and nonmetals and compare their properties. Problem How can you use properties to tell metals from nonmetals? Materials samples of carbon, magnesium, aluminum, sulfur, and tin dishes for the samples Procedure 1. Prepare a table in your Science Journal like the one shown. 2. Observe and record the appearance of each element sample. Include its physical state, color, and whether it is shiny or dull. 3. Remove a small sample of one of the elements. Place it on a hard surface chosen by your teacher. Gently tap the sample with a hammer. The sample is malleable if it flattens when tapped and brittle if it shatters. Record your results. 4. Repeat step 3 for each sample. 5. Test the conductivity of each element by touching the electrodes of the conductivity tester to a sample, as shown in the photo. If the bulb lights, the element conducts electricity. Record your results. Analyze 1. Which elements showed properties of metals? 2. Which elements showed properties of nonmetals? 3. Which elements, if any, showed properties of both metals and nonmetals? Conclude and Apply 4.

Locate each element you used on the periodic table. Compare your results with what you would expect from the location of each element. 5. Locate palladium, Pd, on the periodic table. Use the results of the activity to predict some of the properties of palladium. 6. Infer why some elements may show both properties of metals and properties of nonmetals. 345 allotrope Objectives Distinguish among metals, nonmetals, and metalloids in Groups 13 through l b of the periodic table. Describe the nature of allotropes. Recognize the significance of differences in crystal structure in carbon. Locating the Mixed Groups Can an element be both a metal and a nonmetal? In a sense, some elements are. They are the metalloids, and they have both metallic and nonmetallic properties. A metalloid may conduct electricity better than many nonmetals but not as well as some metals. In the periodic table, the metalloids are the elements located along the stair-step line. The mixed groups- 13, 14, 15, and 16ï¿½contain metals, nonmetals, and metalloids.

The Boron Group Boron, a metalloid, is the first element in Group 13. If you look around your home, you may find two compounds of boron. One of these is boric acid, a mild antiseptic. The other is borax, which is used in laundry products to soften water. Less familiar are the boranes, which are compounds of boron used in fuels for rockets and jet airplanes. Aluminum, a metal, is also in Group 13. Aluminum is the most abundant metal in Earth's crust. Aluminum is used in soft-drink cans, foil wrap, and cooking pans. You may also see aluminum on the sides of buildings. And because aluminum is both strong and light, it is used to build airplanes. When you operate electronic equipment, such as the calculator shown in Figure 12-18, you may be using one of the other metals in Group 13. These metals are gallium, indium, and thallium, used to produce semiconductors. Semiconductors conduct an electric current under certain conditions. You will learn more about semiconductors in Chapter 23.

Figure 12-18 Calculators contain semiconductors. What metals from Group 13 are used to produce semiconductors? 346 The Carbon Group Each element in Group 14, the carbon family, has four electrons in its outer energy level. But this is where much of the similarity ends. Carbon is a nonmetal; silicon and germanium are metalloids; tin and lead are metals. What do the diamond in a diamond ring and the graphite in your pencil have in common? It may surprise you to learn that they are both carbon. How can this be? Diamond and graphite are examples of allotropes. Allotropes are different forms of the same element having different molecular structures. Look at Figure 12-19. Graphite is a black powder that consists of hexagonal layers of carbon atoms. In the hexagons, each carbon atom is bonded to three other carbon atoms. The fourth electron of each atom is bonded weakly to the layer next to it. This structure allows the layers to slide easily past one another, making graphite an excellent lubricant. Figure 12-19 Two allotropes of carbon are graphite (A) and diamond (B).

What geometric shapes make up each allotrope? 347 Problem Solving Waiting to Be Discovered In sports, the "Rookie of the Year" award typically designates a player who had an outstanding first year and shows great potential for continued achievement. Most of the selections live up to that expectation, but not all. At the beginning of the 1990s, Science magazine selected Buckminsterfullerene as the "Molecule of the Year." This allotrope of carbon was isolated by R.E. Smalley when some carbon materials were subjected to laser bursts. Later, the carbon condensed into unusual spherical elements. The tiny spheres were later shown to be made of 60 carbon atoms arranged in an open cage that could resemble a hollow soccer ball. Many new uses of this third allotrope were thought possible. Interesting medical applications were proposed to attach special disease-attacking components to the outside of the molecule. Another idea was to insert radioactive atoms inside the cage. They could then be injected inside a patient to arrive at a specific site. Another problem the new molecule could solve is the separation of mixtures. Buckminsterfullerene molecules, also called Buckyballs, can be packed into containers and used as separating sieves.

Solve the Problem: 1. Use a tall cylinder of glass marbles to represent Buckminsterfullerene molecules, and a mixture of sand or salt and small BB pellets to represent a mixture of chemical compounds. 2. Pour the sand and BB mixture over the marbles. Think Critically: 1. How did the packing and spacing of the spherical marbles enhance the separation of your mixture? 2. How could Buckyballs be used to separate compounds? 3. Can you think of other potential uses for this molecule? USING MATH A tetrahedron is a polyhedron with four congruent faces, each of which is an equilateral triangle. Use the figure below as a pattern and make a tetrahedron out of paper. Tough Tetrahedrons A diamond is clear and extremely hard. In a diamond, each carbon atom is bonded to four other carbon atoms at the vertices, or corner points, of a tetrahedron. In turn, many tetrahedrons join together to form a giant molecule in which the atoms are held tightly in a strong crystal structure. This structure accounts for the hardness of diamond. Carbon occurs as an element in coal and in compounds in oil, natural gas, and foods.

Carbon in these materials may combine with oxygen to produce carbon dioxide, CO2. In the presence of sunlight, plants utilize CO2 to make food. In Chapter 13, you will study other carbon compoundsï¿½ many essential to life. 348 Silicon is second only to oxygen in abundance in Earth's crust. Most silicon is found in sand, silicon dioxide, SiO2, and in almost all rocks and soil. The crystal structure of silicon dioxide is similar to the tetrahedrons in diamond. Silicon occurs as two allotropes. One of these is a hard, gray substance, and the other is a brown powder. Both silicon and germanium, the other metalloid in the carbon group, are used in making semiconductors, which you'll learn about in Chapter 23. Tin and lead are typical metals. Tin is used to coat other metals to prevent corrosion. Tin is also combined with other metals to produce bronze and pewter. Lead was once used widely in paints and antiknock gasoline. However, lead is poisonous, so it has been replaced in these materials. The Nitrogen Group The nitrogen family makes up Group 15. Each element has five electrons in its outer energy level.

These elements tend to share electrons and to form covalent compounds with other elements. Each breath you take is about 80 percent gaseous nitrogen, in the form of diatomic molecules, N2. If you look again at Figure 12-10 on page 340, you'll see that nitrogen is the element fourth in abundance in your body. Yet you and other animals and plants can't use nitrogen as N2. The nitrogen must be combined into compounds, such as nitratesï¿½compounds that contain the nitrate ion, NO3-. Much nitrogen is used to make nitrates and ammonia, NH3, both of which are used in fertilizers. Figure 12-20 The carbon group includes lead and tin. A Most gasolines are no longer leaded. B Pewter contains tin and other metals. Why would dishes made of lead be dangerous? 349 Phosphorus is a nonmetal that has three allotropes. Uses of phosphorus compounds range from water softeners to fertilizers to match heads. Antimony is a metalloid, and bismuth is a metal. Both elements are used with other metals to lower their melting points.

It is because of this property that the metal in automatic fire-sprinkler heads contains bismuth. The Oxygen Group The oxygen group makes up Group 16 on the periodic table. You can live for only a short time without the nonmetal oxygen, which makes up about 20 percent of air. Oxygen exists in the air as diatomic molecules, O2. During electrical storms, some oxygen molecules, O2, change into ozone molecules, O3. Do you notice that O2 and O3 are allotropes? Nearly all living things on Earth need free oxygen, as O2, for respiration. Living things also depend on a layer of ozone, O3, around Earth for protection from some of the sun's radiation, as you will learn in later chapters. The second element in the oxygen group is sulfur. Sulfur is a nonmetal that can exist in allotropes as different-shaped crystals and as a noncrystalline solid. In Figure 12-21, you see a magnified view of two different crystalline allotropes of sulfur. Sulfur combines with metals to form sulfides of such distinctive colors that they are used as pigments in paints.

The nonmetal selenium and two metalloids, tellurium and polonium, are the other Group 16 elements. Selenium is the most common of these. This element is one of several that 350 you need in trace amounts in your diet. Many multivitamins contain this nonmetal as one of their ingredients. In Figure 12-22, you can read the label and find other elements present in vitamins. Selenium can be toxic if there is too much in your system. Figure 12-21 Sulfur is typically a bright yellow nonmetal. One allotrope of sulfur has eight-sided crystals. The other allotrope has a needlelike crystal. What is an eight-sided object called? Figure 12-22 Selenium is one of several elements needed by the body in trace amounts. Section Wrap-up Review 1. Why are Groups 14 and 15 better representatives of mixed groups than are Group 13 or Group 16? 2. How do the allotropes of sulfur differ? 3. Think Critically: Why is graphite a lubricant while a diamond is the hardest gem known?

Skill Builder Concept Mapping Make a concept map for allotropes of carbon, using the terms graphite, diamond, buckminsterfullerene, sphere, hexagon, and tetrahedron. If you need help, refer to Concept Mapping in the Skill Handbook. Science Journal In your Science Journal, write a paragraph in which you discuss the term valuable when applied to an element. Consider rarity, usefulness, and durability. 351 Design Your Own Experiment Slippery Carbon Often, a lubricant is needed when two metals touch each other. For example, a sticky lock can sometimes work better with the addition of a small amount of graphite. What gives this allotrope of carbon the slippery property of a lubricant? PREPARATION Why do certain arrangements of atoms in a material cause the material to feel slippery? Form a Hypothesis Based on your understanding about how carbon atoms bond, form a hypothesis about the relationship of graphite's molecular structure to its physical properties. Objectives Make a model that will demonstrate the molecular structure of graphite. Compare and contrast the strength of types of bonding in graphite. Infer the relationship between bonding and physical properties. Possible Materials Use care when working with scissors, sharp toothpicks, and spaghetti.

352 PLAN THE EXPERIMENT 1. As a group, agree upon a logical hypothesis statement. 2. As a group, sequence and list the steps you need to test your hypothesis. Be specific, describing exactly what you will do at each step to make a model of the types of bonding present in graphite. 3. Remember that graphite consists of rings of six carbons in a flat hexagon. These rings are interconnected. In addition, the flat rings in one layer are weakly attached to other flat layers. 4. Make a list of possible materials you plan to use. Check the Plan 1. Read over the entire experiment to make sure that all steps are in logical order. 2. Will your model be constructed with materials that show both weak and strong attractions? 3. Make sure your teacher approves your plan and that you have included any changes suggested. DO THE EXPERIMENT 1. Have you selected materials to use in your model that demonstrate both weak and strong attractions? 2. Once your model has been constructed, write down any observations that you make and include a sketch for your Science Journal. Analyze and Apply 1. Compare your model with designs and results of other groups. 2.

How does your model illustrate two types of attractions found in the graphite structure? 3. How does the bonding in graphite explain graphite's lubricating properties? Write your answer in your Science Journal. Go Further Oils are used on bike chains, engine parts, and other areas where metals touch. Find out how these lubricants work. 353 Science and Art Pottery and Clay In this chapter, you found out that the element hydrogen makes up nearly 90 percent of the universe. However, 82 percent of Earth is made up of oxygen, silicon, and aluminum. The clays formed by these three elements have been used by people for nearly 7000 years. Pottery clay is approximately 40 percent aluminum oxide, 46 percent silicon oxide, and about 14 percent water. The presence or absence of impurities in clay creates the wide variety of pottery from delicate, porcelain Chinese teacups to Hopi earthenware pots. Stains and Glazes Prehistoric potters did little to change or enhance the colors of their works of art.

Glazes, or glassy coatings, appeared about 2700-2100 B.C., when Persian and Egyptian potters made pastes of quartz and sand mixed with either copper or manganese. Copper glazes left the ceramics turquoise, and manganese glazes made them violet or purple. Today, many artists use metal oxides to enhance or even alter the basic color of the clay. Wedgwood jasperware gets its blue color from an oxide of cobalt. Iron oxides, often present in clay, provide the earthy red and brown tones common among Native American pottery. Firing Firing is the application of heat to a piece of pottery. In oxidized firing, a kiln, or oven, rich in oxygen allows the combination of metals within the clays and the glazes through combustion. This results in clean, unspotted pottery. Reduction firingï¿½firing with no oxygen presentï¿½takes place in a kiln fueled by natural gas, wood, or oil, and leaves a characteristic speckled look. Different colors can be obtained from the same glazes. Reduction firing of copper oxide glazes will produce a deep, blood-red color.

When the same glazes undergo oxidized firing, various shades of green are produced. Science Journal Design a simple piece of pottery and describe in your Science Journal the methods and glazes you would use to produce your finished look. 354 Summary 12-1: Metals 1. A typical metal is a hard, shiny solid thatï¿½ due to metallic bondingï¿½is malleable, ductile, and a good conductor. 2. Groups 1 and 2 are the alkali and alkaline earth metals, which have some similar and some contrasting properties. 3. The iron triad; the coinage metals; and the zinc, cadmium, and mercury group are among the transition elements, which make up Groups 3-12 on the periodic table. 12-2: Science and Society: New Elements, New Properties 1. The lanthanides and actinides have atomic numbers 58-71 and 90-103, respectively, whereas transuranium elements have atomic numbers greater than 92. 2. The making of synthetic elements with rio immediate practical use is controversial. 12-3: Nonmetals 1.

As a typical nonmetal, hydrogen is a gas that forms compounds by sharing electrons with other nonmetals and also with metals. 2. All the halogens, Group 17, have seven outer electrons and form both covalent and ionic compounds, but each halogen has some properties unlike the others. 3. The noble gases, Group 18, are elements whose properties and uses are related to their chemical stability. 12-4: Mixed Groups 1. Groups 13 through 16 of the periodic table include metals, nonmetals, and metalloids. 2. Allotropes are forms of the same element having different molecular structures. 3. The properties of three forms of carbonï¿½ graphite, diamond, and buckminsterfullereneï¿½depend upon the differences in their crystal structures. Key Science Words a. allotropeï¿½ï¿½ï¿½ b. diatomic molecule c. ductileï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ d. malleableï¿½ e. metallic bondingï¿½ï¿½ f. radioactive element Choose the word or phrase that completes the sentence or answers the question.

1. When magnesium and fluorine react, what type of bond is formed? a. metallicï¿½ï¿½ï¿½ï¿½ b. ionic c. covalentï¿½ï¿½ï¿½ d. diatomic 2. What type of bond is found in a piece of pure gold? a. metallicï¿½ï¿½ï¿½ï¿½ b. ionicï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ c. covalent d. diatomic 3. Because electrons move freely in metals, metals areï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ a. brittleï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ b. hardï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ c. dull 4. The _____ make up the most reactive group of all metals. a. iron triadï¿½ï¿½ b. coinage metals 5.

The most reactive of all nonmetals is a. fluorineï¿½ï¿½ï¿½ï¿½ b. uraniumï¿½ï¿½ï¿½ï¿½ c. hydrogen 6. The element _____ is always found in nature combined with other elements. a. copperï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ b. goldï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ c. magnesium 7. The least magnetic of these metals is a. cobaltï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ b. ironï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ c. nickel d. titanium 8. When neptunium atoms fall apart, they formï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ a. ytterbiumï¿½ Understanding Concepts Answer the following questions in your Science Journal using complete sentences. 11.

Reading from top to bottom on the periodic table, metallic properties of elements increase; reading from left to right, metallic properties decrease. Which element is the most metallic of all? Explain your answer. 12. The most abundant elements in Earth's crust are a nonmetal, a metalloid, and two metals. List the four elements. 13. Why do oxygen and nitrogen occur in the air as diatomic molecules, but argon, neon, krypton, and xenon occur as single atoms? 14. Explain why hydrogen, a nonmetal, is on the metal side of the periodic table. 15. Name three metals used to coat other metals. Why is one metal used to coat another? Thinking Critically 16. Why was mercury used in clinical thermometers, and why is it no longer used for that purpose? 17. The density of hydrogen is so low that it can be used to fill balloons to make them lighter than air. Why is helium used more frequently? 18. Why is aluminum used instead of steel in building airplanes? 19. Why are silver compounds used in photography? Name two nonmetals extracted from seawater that are also part of these compounds. 20.

Like selenium, chromium is poisonous but is needed in trace amounts in your diet. How does this information apply to the safe use of vitamin-mineral pills? 356 Developing Skills If you need help, refer to the Skill Handbook. 21. Making and Using Tables: Use the periodic table to classify each of the following as a lanthanide or actinide: californium, europium, cerium, nobelium. 22. Comparing and Contrasting: Aluminum is close to carbon on the periodic table. Explain why aluminum is a metal and carbon is not. 23. Observing and Inferring: You are shown two samples of phosphorus. One is white and burns if exposed to air. The other is red and burns if lit. Infer why the properties of two samples of the same element differ. 24. Recognizing Cause and Effect: Plants need nitrogen compounds. Nitrogen fixing changes free nitrogen into nitrates. Lightning and legumes are both nitrogen fixing. What are the cause and effect of nitrogen fixing in this example? 25. Concept Mapping: Complete the concept map below for some common metals. You may use symbols for the elements. Performance Assessment 1.

Analyzing the Data: The model you made in Activity 12-2 on pages 352-353 helps explain the lubricating ability of graphite. Use that same model to explain how the graphite in a pencil is able to leave a mark on a piece of paper. 2. Investigating an Issue Controversy: Research the pros and cons of using nuclear energy to produce electricity. Prepare a report that includes data as well as your informed opinion on the subject. If several class members do research, conduct a debate on the issue. 3. Newspaper Article: Research the source, composition, and properties of asbestos. What properties made it suitable for use in construction in the past? How did these same properties cause asbestos to become a health hazard, and what is being done now to eliminate the hazard? Write a newspaper article that shares your findings with the public. 357

Question: Reading down group 1 (alkali metals) on the periodic table, the symbols for elements 3 and 11 form the name of which Chinese tennis player?
Answer: Li Na